1. Technical Field
This invention relates generally to prosthetics, and more particularly to a new and improved replacement ligament.
2. Background Information
Replacement ligaments can restore performance where native structures rupture beyond repair. But success depends on proper attachment to the host bone. Thus, the manner in which this is done and the related details of prosthesis construction are important.
Consider, for example, an injured knee joint having a damaged anterior cruciate ligament. Attachment of a replacement ligament according to existing techniques may involve forming tunnels in the femur and tibia (the host bones). The tunnels are formed so that each extends through one of the host bones from an entrance or proximal end of the tunnel at the natural ligament attachment site to an exit or distal end of the tunnel at an outer surface of the host bone.
Each end of the replacement ligament is passed through one of the tunnels, from the proximal end to the distal end where it is anchored to the outer surface of the host bone by such means as stapling. This results in the replacement ligament spanning the intra-articular region between the natural attachment sites somewhat like a natural ligament, but it also results in certain problems that need to be overcome.
For example, the replacement ligament extends beyond the natural attachment sites and all the way through the tunnels to the outer surfaces on the other side of each host bone. This results in the replacement ligament being able to stretch over a greater length than a natural ligament (from the outer surface of the femur to the outer surface of the tibia), and this impairs performance.
In addition, formations such as bone spicules can form at the entrance to each of the tunnels. These tend to abrade the replacement ligament, cause fatigue of the material, and break off particles which can cause irritation.
Furthermore, the tunnels provide access to the host bone interior. As a result, synovial fluid can migrate from the intra-articular region between host bones into the bone tunnels. Thus, any activity in the intra-articular region, such as infection, can be easily communicated into the bone interior and result in intra-osseous complications. Similarly, activity within the bone can be easily communicated to the intra-articular region.
Consequently, it is desirable to have a new and improved replacement ligament and attachment method that overcomes these concerns.